Thermally responsive switching device



Nov. 3, 1964 s. R. Mn'lcK, JR 3,155,799

THEEMALEY RESPONSIVE swITcHING DEVICE Filed Jan. 2, 1963 2 Sheets-Sheet 1 Nov. 3, 1964 s. R. MmcK, .1R 3,155,799

TEEEMAELY RESPONSIVE swITcHING DEVICE Filed Jan. 2, 1963 2 Sheets-Shea*` 2 United States Patent O 3,155,799 THERMALLY RESPGNSiVlE SWITCHHNG DEE/'ECE Stanley R. lditiclr, Ir., Morrison, ill., assigner to General Electric Company, a corporation of New York Filed Jan. 2, i963, Ser. No. 248,995 7 lairns. (Cl. 2Mb-133) rThis invention relates to thermal switching devices and has particular application to that class of switching devices utilized with warm air furnaces.

Conventional warm air furnace systems generally include a temperature responsive control device, located in the plenum chamber of the furnace, to control the operation of the fan which circulates the warmed air throughout the area to be heated. It is desirable that such a control device should be extremely reliable, while also including a manual adjustment means for varying the control level or point at which the control device can be actuated by a condition responsive element. An important object ot the present invention is to provide an improved thermally responsive switching device which is simple and economical in construction, reliable in operation and includes an efficient adjustment means for varying the control level at which `the device can be actuated.

It is another object of this invention to provide an improved thermally responsive switching device which includes an accurate and inexpensive adjustment means for varying the control level at which the device can be actuated.

it is a further object of my invention to provide a thermally responsive control device which is of rugged construction and very eflicient in operation.

It is a further object of my invention to provide an irnproved thermally responsive device which includes a manual adjustment means for maintaining the device in the same condition over a prolonged period.

In carrying out one aspect of my invention, in one form thereof, I apply it to a thermally responsive control device for use in a warm air furnace. This device includes a supporting frame, a self-contained switch positioned on one side of the frame, and a bimetal disposed on the other side of the frame. One end of the bimetal is operatively connected with the switch. The other end of the bimetal is carried by one end of a carriage member which is supported on and movable relative to the frame. This carriage member extends on both sides of the frame and it is continuously biased toward the end thereof which carries the bimetal. A cam is rotatably supported on the carriage member at the end thereof opposite the bimetal. This cam is arranged on the carriage member to rotate about an axis transverse to the direction of movement ot the carriage member. The cam has a lever arm integral thereto and it is arranged to manually adjust the longitudinal position of the carriage member relative to the frame. Rotation of the cam thus adjusts the position of the bimetal relative to the switch for varying the temperature level at which the switch is actuated by the bimetal. Such an adjustment arrangement for the device is very simplified and economical in construction.

By `a further aspect of my invention, I provide an improved arrangement for biasing the carriage member toward the bimetal. This improved arrangement may, of course, be combined with the aforesaid structure to provide a particularly desirable thermally responsive control device. In this arrangement, a tension spring is stretched between a notch formed on the carriage member, and part of the frame, in such a manner that its biasing force pulls the cam toward the frame and also pulls the carriage member into Aa precise bearing engagement with the frame.

Further aspects of my invention will become apparent hereinafter, and the specification concludes with claims ICC particularly pointing out and distinctly claiming the subject matter which I regard as my invention. The invention, however, as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description when taken in conjunction with the accompanying drawings, in which:

FIG. l is a side elevational View of la thermally responsive switching device embodying my invention;

FG. 2 is a left end View of the device shown in FIG. l;

FIG. 3 is a side elevational view of the device of FIG. l, showing the opposite side thereof;

FIG. 4 is a top view of the device as shown in and FIG. 5 is an exploded and fragmentary perspective view of the thermally responsive device.

Referring first to FIGURES 1-4, the temperature control arrangement includes a generally U-shaped channel 10 having side sections i2, i3 (FIG. 2) and connecting portion 1d. Each of the side sections 12 and 13 has a pair of spaced apart tongues le formed on its upper end (viewing FIGS. l-3). The tongues 16 on the side sections 12 and 13 are extended upwardly through suitable slots form-ed in a. supporting plate i8, and the sections l2 and i3 are staked to plate l@ as indicated at 2li in FIGS. l and 3 to form a rigid supporting frame for the operating mechanism of the device.

To make the desired circuit connections for the control device, a self-contained switch unit 22 has been provided. This switch unit 22 is secured to the supporting frame above plate i8 by placement between opposed pairs of the tongues l5 of the channel l@ (FIG. 4), the extension of screws 2d through aligned apertures of the tongues 16 and the switch housing 32., and the threaded engagement of nuts 26 with the ends 23 of the screws opposite to their heads 3d. The threaded ends 2S of the screws 2d are also extended through spacers 3l, which are sandwiched by the screws between inner surfaces of associated tongues I6 of the channel, and an adjacent outer surface of the switch housing 32 (FIG. 4).

The switch unit 22 is of the well known self-contained snap acting type, and in the particular illustrated embodiment it includes an insulative box-shaped housing 32 having terminals 34, 36 for the contacts (not shown) extending outwardly from its opposite ends (FIGS. 1 3). To effect the operation of the contacts of the switch unit 22 between their open and closed positions, as shown in FIGS. 2 and 3, an actuating button 38 is extended outwardly and downwardly through the switch housing 32. The button 3S is normally spring biased to its outermost position by a suitable means within the switch, and when button 38 is in its outermost position the switch contacts are engaged to close a circuit between the terminals 34 and 3S.

FIG. l;

Turning now to a discussion of the thermally responsive means for actuating the switch unit 22:, attention is further directed to FIGS. 2 and 3. On the bottom side of the plate 18 (FIG. 3) and in spaced relation thereto, there is provided a U-shaped bimetal 4t). One end 42 of the bimetal d@ is rigidly attached to `and supported by the turned over end 4d of an L-shaped carriage member 46. The free end 43 of bimetal 4i) is operatively attached to the bottom end 45a of an elongated operating rod 4S, the upper end 45t: of which (FIG. 2) is normally in operative engagement with the actuating button 38. The stem t8 of the carriage member de is guided for sliding movement within generally rectangular slots 49 formed in the supporting plate i8 (FlG. 2), and in a turned over portion Sil (FIG. 5) of a downward extension 52 of side section I3 of the channel iti. To enchance t le strength of the carriage member 46 a longitudinal rib 54 is formed in stem 48.

Turning now to an important aspect of the present invention, which concerns a simplified and etlicient means for manually setting the control point or response level at which the switch 22 can be actuated by the bimetal 40, attention is directed to FIG. 5. Near the upper end 53 of the slidable carriage member e6, which is disposed between a pair of tongues I6 on one side of the switch housing 32 (FIG. l), a combination cam and setting lever member dll is rotatably supported on stem 48. The cam and setting lever member d@ is constructed as a single generally flat piece of metal, and it includes cam section 62, setting arm 63 which extends outwardly in radial fashion from cam section 62, and stop tab 65. The cam section 62 0f memberdl is attached to the outer surface of stern 48 of carriage member i6 by extending a shoulder rivet 6d through an aperture of section d2 and an aligned aperture in the stem lil and then turning over the shanked end ofthe rivet on the inner surface of stem As shown in FIG. 4, a spring washer 6d is itted around the shoulder rivet 64 and is in compression between member d@ and stem i8 of carriage member 46. The spaced relationship between the cam section o2 of member 3G and the stem 48, which is provided by the shoulder rivet de and spring washer 66, permits the cam section 62 to rotate on the rivet 64 and chanf'e its angular relationship with respect to carriage member de. In addition, the spring 66 exerts a compressive force normal to the head of the rivet 6d to provide a controllable torque which may be suitably maintained for permitting the simplified setting of the cam section 62 to the desired control response.

The cam section 62 of rotatable member o@ is thus positioned on stem 48 oi the carriage member 46 for rotative movement about an axis which is perpendicular to the general plane of stem t3 and also perpendicular to the direction of movement of the operating rod 45. To limit the rotative movement of cam and lever member du, the aforementioned stop tab 65 has an L-shaped conguration (FIG. 4). The turned over end of tab 65 extends through a notch d'7 (FIG. 1) cut out of the right edge (FIG. 5) of carriage member stern 4S. The angularly spaced side edges 67a and @7b of notch 67 limit the rotation of member all to the desired amount, thereby assuring operation within the design range of the control. Directly underneath curved camming edge 62a (FIG. l) of the cam section 62, there is positioned a calibration screw 63. The screw 63 is arranged in threaded engagement with plate I8, and head lll of screw d8 is disposed in partially underlying contiguity to camming edge 62a of the member dll. The purpose of such an arrangement, as shall be further understood hereinafter, is to enable camming edge 62a of the lever dt* to rotatably act upon head 7@ of the calibration screw 68 to raise or lower carriage member E6 in its guiding slots for setting the desired switch operating temperatures.

To maintain a desired torque on screw oil and thus control the frictional resistance to its rotation inplate Id, a tension nut 72 is used on the threaded shank of screw 68 between plate 1S and head 7d.

To help effectively control the sliding movement of stern 48 of the carriage member 46 in its bearing slots 4S, as shown in FIGS. 2 and 5, an elongated tension spring 74 has been provided. The spring 7d is of the helical type, and its hooked ends 74a and lb, respectively, are secured t an anchor tab 76 formed on extension :'52 of channel I0, and a notch '7S formed on the right edge dita of stem 43 (viewing FIG. 5 The spring 74 is continuously stretched in tension as illustrated in FIGS. 2, 3 and 5, with hooked end 'Mb secured to the elongated edge 48a of stem 48 furthest away from the edge 52a of channel extension 52 upon which anchor tab 76 is disposed. In addition, from viewing FIGS. 2 and 3 it will be noted that anchor tab 76 is located a considerable distance downwardly from the notch 78. It will thus be noted that, as shown in FIGS. 2 and 3, spring "lll is in eitect diagonally wrapped around the inner flat side of stem @l With Such an arrangement, the tension spring '7d provides a component of force which pulls camming edge 62a into continuous Contact with the upper face of the head ill or the calibration screw d and it also provides a force component which pulls stem ld of the carriage member do into Contact with the ends 49a (FIG. 5) of the guiding slots fifa?. In addition, the arrangement of spring 7d also provides the exertion of a twisting force on the stem dit which causes it to rotate into a xed relationship with the guiding slots 49. By arranging the tension spring 7d in the aioredescribed manner, assurance is provided that the carriage member will always be in the same position under normal operating conditions, and excellent control repeatability is achieved.

As shown in FIG. 4, on the top of insulating base 32 of switch 22, there is attached a suitable temperature scale titl. The scale dit provides suitable graduations for alignment of the turned over end of setting arm o3 of member 6d, to set the desired temperature response for the switch.

Turning now to another aspect of the present invention which concerns itselt` with a new and improved adjustment means for setting the switch 22 to either on or automatic operation, attention is directed to FIGS. 3 and 5. As shown therein, my improved control device includes a pivotally mounted lever gli, a pivotally mounted actuator 92 which is manually operated by lever 9d, and a spring 9d which is secured to actuator 92 and arranged to maintain it in a normal position. More particularly, the lever @il is pivotally mounted upon a switch supporting screw 3@ located near the right side of the switch (viewing IG. 3). An annular shoulder spacer @o (FIG. 2) is sandwiched between the inner surface of lever 9@ and an adjacent surface of one of the tongues lo, t permit relatively tree pivotal movement of lever @d between the head of iis associated screw Bil and a tongue le of the channel lil. As shown in FIGS. 3 and 5, the lever 9) has an L-shaped setting arm 98. Detent notches Ill@ and Ill?. are formed in angularly spaced apart relationship on one side of a segment shaped body or the lever 9d. The purpose and eifect of notches Intl and Ill?. shall become apparent hereinafter.

As shown in FIG. 5, the actuator 92 is an elongated element which includes a flat body and elongated section lit. An apertured lange MI5 is formed upwardly from one of the side edges of section Idd near the right end thereof (viewing FIG. 5), and a lateral tongue fill@ extends outwardly rorn t-e other side edge of section lll between its ends. An upwardly curved section Ille is formed on the left end of body section (viewing FIG. 5). The actuator 92 is pivotally mounted upon the switch supporting screw Si) located near the left side of the switch (viewing FIG. 3) by placement of the associated screw .lll through the aforementioned aperture oi' dange M5. An annular shoulder spacer Il@ is sandwiched between the inner surface of flange and an adjacent surface of another tongue Id, to permit relatively free pivotal movement of actuator 92 between the head of its associated screw 3@ and a tongue I6 of the channel lil.

As shown in FIGS. 3 and 5, the actuator 92 is pivotally supported upon its associated tongue I6 so that the lateral tongue IM of the actuator extends over the enlarged head formed on the upper end 4519 of operating rod 45, and the curved section Idd of the actuator is engageable by the notches lil@ and M32 or the lever 9d. The spring 94 is of the elongated leaf type, being suspended in cantilever fashion from the pivotally supported end of actuator 92 (as shown in FIG. 3). A curved nose 94a of the spring 94 engages base plate 1 3 to impart a biasing force upon the actuator 92, normally urging the lateral tongue Ill@ upwardly and away from the head of the operating rod 4S.

In operation, when the lever Ml is in the position shown in full in FIG. 3 (and also in FIG. 2), the lateral tongue Ido of actuator 92 is spaced apart by a gap and operatively disengaged irom the enlarged head of the operating rod 45. This is referred to as the automatic position for the lever 9h, since the bimetal dit is freely capable ot operating the button 38 of switch unit 22 in response to temperature variations. The lever tl is detented or held in this position by the engagement of the curved section lltl of the actuator 92 with notch im and the biasing force of spring 9d imparted thereby to the actuator 92 in a counterclocliwise direction (viewing FIG. 3).

When the lever 9d is rotated in a counterclockwise direction of rotation from its automatic position in FIG. 3 to its dotted position, the curved section ltlS or" the actuator 92 is cammed by the lever 9d into the detent notch ldd, causing the actuator tongue ldd to hold the enlarged head of the operating rod d5 away from the actuating button 3S of the switch unit 22. With the device in this condition, the switch contacts are in their normally closed position to operate the device controlled, such as a fan being used in the summertime, for a continuous period. This position is called the on position, since the bimetal itl is incapable of operating the button of switch unit 22 in response to temperature variations. The lever 9i) is detented or held in this position by the engagement of the curved section dit? of the actuator 9?; with notch lith. When the lever 9d is in its on position the detent notch lltiti cooperates with the curved section to provide an effective self-locking action which maintains the operating rod l5 in spaced apart relationship to the switch button 3S, regardless of the magnitude of torce applied to rod d5 by the bimetal t?.

By using the lever 9d, actuator 92, and spring 94- in the manner described, a simple and expeditious means is thereby achieved to selectively set the switch unit 22 for automatic or continuous on type operation.

Turning now to a description of the overall thermally responsive operation of the improved switching device ofthe present invention, attention is directed to FIGS. 1 4. For normal operation, as illustrated in FIG. 4, setting arm 63 of the rotatable cam and lever member oil is in a fixed position, and cam section o2 of the member dit is biased by tension spring 7d into engagement with calibration screw titi. The angular position of cam section 62, which is rotatably supported on carriage member d6, maintains the Xed end 42 of bimetal d@ in a certain spaced relationship with switch actuating button 3d. in the illustrated device, as shown in FltG. l, the high eX- pansion side of the bimetal 4d is disposed on the outside of the U-shaped conguration. As temperature sensed by the bimetal d@ increases, the free end i3 thereof moves away from switch unit 22 (i.e., downwardly viewing FlGS. 1-3), thereby allowing the actuating button 33 to move downwardly to its free position. The normally closed contacts ot the switch unit 22 are thereupon snapped to a closed position and a circuit is closed across the terminals 3d, 3d to energize a device which is to be controlled, such as a ian motor. As the temperature sensed by the bimetal fili decreases, the tree end d3 of the bimetal moves toward the switch (i.e., upwardly viewing FlGS. 1 3), thereby causing the operating rod 45 to depress (i.e., push up, in FiGS. 2 and 3) the actuating button 3d of the switch unit 22. The upward movement of operating rod d5 thus snaps the normally closed contacts of witch unit 22 to their open position, deenergizing the circuit connected across terminals 34, 36 to turn oit the controlled device.

For setting the desired operating temperatures' for the controlled device, the setting arm 63 of the combined cam and lever member @il is rotated to the desired position relative to temperature scale 8h. The cam section 62 thereupon acts upon the head '7h of calibration screw 6d to slide the carriage member d6 in its bearing slots d. The sliding movement of carriage member d6 changes the space relationship between the supported end 4t2, of bimetal d@ and the switch actuating button 33. This sets the desired level of temperature response for the operation of switch unit 22.

For calibrating the improved control device of the present invention during the manufacture thereof, the setting lever titl is placed in a predetermined position and, with the bimetal dit in a liquid bath or some other suitable substance winch is at the same temperature indicated on the scale Sh, the calibration screw 63 is rotated until the switch operates to its off position.

It will now, therefore, be seen that my new and improved thermally responsive switching device as herein illustrated provides a simple and efcient means for varying the control level at which the device can be actuated. It will also be realized that my improved thermally responsive control device is simple in construction and in overall operation.

While in accordance with the Patent Statutes, I have described what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that Various changes and modications may be made therein without departing from my invention, and l, therefore, aim in the following claims to cover all such equivalent variations as fall within the true spirit and scope of this invention.

What l claim as new and desire to secure by Letters Patent of the United States is:

l. A temperature responsive device for use in a heating system, said device comprising a support, a switch positioned on said support, an elongated carriage member arranged for sliding movement relative to said support, a bimetal having one end fixed to said carriage member, means operatively connecting the other end of said bimetal with said switch, a first adjustable means for selectively connecting and disconnecting said last mentioned means from said switch, and a second adjustable means supported on said carriage member for manually adjusting the longitudinal position of said carriage member relative to said support, thereby to adjust the position of said bimetal and the temperature level at which said switch is activated by said bimetal.

2. The temperature responsive device of claim l wherein the rirst adjustable means includes a rotatable lever and a spring biased actuating element selectively and cooperatively engageable with said lever to operatively connect and disconnnect the bimetal from the switch.

3. A temperature responsive device for use in a heating system, said device comprising a support, a switch positioned on said support, an elongated carriage member arranged for sliding movement relative to said support, a bimetal having one end ixed to said carriage member, means operatively connecting the other end of said bimetal with said switch, a spring biased actuator mounted for rotation upon said support, a first lever' mounted for rotation upon said support, said lever having an angularly spaced apart pair of notches formed therein, the notches of said iirst lever being arranged to selectively act upon said spring biased actuator for connecting and disconnecting said connecting means from said switch, and a second lever rotatably supported upon said carriage member, said second lever having a cam portion formed therein, said cam portion of said second lever being arranged to act upon said support in response to the angular position of said second lever, thereby to adjust the position of said bimetal and the temperature level at which said switch is actuated by said bimetal.

4. A. temperature responsive device for use in a heating system, said device comprising a supporting frame, a unitary switch positioned on one side of said frame, a plurality of bearing slots formed in said frame, lan elongated carriage member arranged in said bearing slots and extending on both sides ot said frame for sliding movement relative thereto, a bimetal having one end xed to said carriage member on the side or" said frame opposite the switch, means operatively connecting the other end of said bimetal with said switch, a cam rotatably supported by said carriage member on the same side of the frame as said switch and being slidable with said carriage member,

said cam being in rotatable engagement with said frame for varying the longitudinal position of said carriage member relative to said frame for adjusting the position of said bimetal, and an elongated spring extending in tension between said carriage member and said frame and disposed on `the same side of said frame as said bimetal, said spring means being Wrapped around one side of said carriage member and disposed in diagonal relationship to the direction of movement of said carriage member thereby to act upon said carriage member for biasing said slidable carriage member into precise engagement with said bearing means.

5. A temperature responsive device for use in a heating system, said device comprising a support, a switch positioned on said support, a plurality of bearing slots formed on said support, an elongated carriage member in said bearing slots for sliding movement relative to said support, a bimetal having one end :fixed to said carriage member, means operatively connecting the other end of said bimetal with said switch, a rotatable cam supported on said carriage member for varying the longitudinal position of said carriage member relative to said support to adjust the position of said bimetal, and an elongated spring extending in tension between said carriage member and said support for operatively engaging said cam with said support, said spring means being wrapped around one side of said carriage member and disposed in diagonal relationship to the direction of movement or" said carriage member thereby to bias said cam into engagement with Said support and to apply a twisting moment to said carriage member for biasing said slidable carriage member into precise engagement with said bearing slots.

6. A temperature responsive device for use in a heating system, said device comprising a support, a switch positioned on said support, a plurality of bearing slots formed on said support, an elongated carriage member arranged in said bearing slots for sliding movement relative to said support, a bimetal having one end xed to said carriage member, means operatively connecting the other end of said bimetal With said switch, a spring biased actuator mounted for rotation upon said support, a iirst lever mounted for rotation upon said support, said lever having an angularly spaced apart pair of notches formed therein, the notches of said irst lever being arranged to selectively n (CB act upon said spring biased actuator for connecting and disconnecting said connecting means from said switch, a second lever rotatably supported upon said carriage member, said second lever having a cam portion formed therein, said cam portion of said second lever being arranged to act upon said support in response to the angular position of said second lever, thereby to adjust the position of said bimetal and the temperature level at which said switch is actuated by said bimetal, and an elongated spring extending in tension between said carriage member and said support, said spring being wrapped around one side of said carriage member and disposed in diagonal relationship to the direction of sliding movement of said carriage member thereby to act upon said carriage member for biasing said member into precise engagement with said bearing slots.

7. A temperature responsive device for use in a heating system, said device comprising a support, a switch positioned on said support, `an elongated carriage member, bearing means mounting said carriage member on said support for sliding movement relative to said support, a bimetal having one end fixed to said carriage member, means operatively connecting the other end of said bimetal with said switch, adjustable means interengageable between said carriage member and said support for varying the longitudinal position of said carriage member relative to said support for adjusting the position of said bimetal, and an elongated spring extending in tension between said carriage member and said support for operatively engaging the adjustable means between said carriage member and said support, said spring means being wrapped around one side of said carriage member and disposed in diagonal relationship to the direction of movement of said carriage member thereby to apply a twisting moment to said carriage member for biasing said slidable carriage member into precise engagement wit said bearing means.

Reterences Cited in the tile of this patent UNlTED STATES PATENTS 2,489,854 Broekman w Nov. 29, 1949 2,848,582 Booth H Aug. 19, 1958 2,878,344 Gustafson et al. Mar. 17, 1959 3,044,295 Shivers july 17, 1962 

1. A TEMPERATURE RESPONSIVE DEVICE FOR USE IN A HEATING SYSTEM, SAID DEVICE COMPRISING A SUPPORT, A SWITCH POSITIONED ON SAID SUPPORT, AN ELONGATED CARRIAGE MEMBER ARRANGED FOR SLIDING MOVEMENT RELATIVE TO SAID SUPPORT, A BIMETAL HAVING ONE END FIXED TO SAID CARRIAGE MEMBER, MEANS OPERATIVELY CONNECTING THE OTHER END OF SAID BIMETAL WITH SAID SWITCH, A FIRST ADJUSTABLE MEANS FOR SELECTIVELY CONNECTING AND DISCONNECTING SAID LAST MENTIONED MEANS FROM SAID SWITCH, AND A SECOND ADJUSTABLE MEANS SUPPORTED ON SAID CARRIAGE MEMBER FOR MANUALLY ADJUSTING THE LONGITUDINAL POSITION OF SAID CARRIAGE MEMBER RELATIVE TO SAID SUPPORT, THEREBY TO ADJUST THE POSITION OF SAID BIMETAL AND THE TEMPERATURE LEVEL AT WHICH SAID SWITCH IS ACTIVATED BY SAID BIMETAL. 